Thinly slice the onion, slice the Thai chilies, and finely mince the garlic.
Separate the Chinese broccoli leaves from the stems. Cut the leaves and stems into roughly ½-inch pieces.
In a small bowl, combine dark soy sauce, light soy sauce, oyster sauce, fish sauce, sugar, and water. Mix thoroughly and set aside.
Heat a large pan or wok over medium-high heat with a bit of oil. Add the onions, garlic, and chilies and cook until fragrant.
Add the chicken and cook until browned and nearly cooked through.
Add the Chinese broccoli stems and cook for about 1 minute.
Add the Chinese broccoli leaves and cook until wilted.
Add the rice noodles and sauce. Toss everything together until the noodles absorb the sauce and are evenly coated.
Finish with the Thai basil and toss until wilted.
Serve in a bowl or enjoy straight from the pan.
